Wireless electric power receiver for wirelessly regulating electric power using switch

ABSTRACT

A wireless electric power receiver for receiving wireless electric power from a wireless electric transmitter is provided. The wireless electric power receiver includes an electric power receiving unit that receives wireless electric power from the wireless electric power transmitter; a rectifying unit that rectifies wireless electric power in the form of alternating current output from the wireless electric power receiving unit and outputs rectified electric power; and an electric power regulation unit that receives an input of the rectified electric power, outputs first electric power which has a lower value of a first voltage than that of the rectified electric power for a first period, and does not output electric power for a second period, so as to output electric power with a predetermined voltage value.

PRIORITY

This application claims priority under 35 U.S.C. §119(a) to KoreanApplication Serial No. 10-2012-0113579, which was filed in the KoreanIntellectual Property Office on Oct. 12, 2012, and Korean ApplicationSerial No. 10-2013-0064146, which was filed in the Korean IntellectualProperty Office on Jun. 4, 2013, the entire contents of each of whichare incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a wireless electric powerreceiver, and more particularly to a wireless electric power receiverfor wirelessly receiving electric power based on an electromagneticresonance scheme.

2. Description of the Related Art

A mobile terminal, such as portable telephones and Personal DigitalAssistants (PDA), is typically operated by a rechargeable battery. Inorder to charge the battery, the battery of the mobile terminal issupplied with electric energy by using a separate charging device.Typically, the charging device and the battery have separate contactterminals on an exterior thereof, respectively, and are electricallyconnected with each other by the contacting their contact terminals.

However, in the contact type charging method, since the contactterminals protrude toward an exterior, the contact terminals may beeasily damaged or become dirty due to alien substances. As a result,there is problem in that the charging of the battery is not properlyperformed. Where the contact terminals are exposed to moisture, thecharging of the battery may not be properly performed.

In order to solve the above mentioned problems, wireless chargingtechnologies or noncontact charging technologies have been recentlydeveloped and utilized for many electronic devices.

In the wireless charging technologies, wireless electric powertransmission and reception techniques are used. For example, when aportable terminal is not connected to a separate charging connector andmerely put on a charging pad, a battery of the portable terminal isautomatically charged. The wireless charging technologies haveadvantages in that electronic products are wirelessly charged resultingin an improvement of a waterproof function, and the portability ofelectronic devices can be improved because a wired charging device isunnecessary. Further, it is forecasted that related technologies willsignificantly grow in the coming electric vehicle era.

The wireless charging technologies generally include an electromagneticinduction scheme using a coil, a resonance scheme using resonance, andan RF/Micro wave radiation scheme in which electric energy is convertedinto microwaves and then transmitted.

Up to now, the electromagnetic induction scheme has become mainstream.Recently, domestic and foreign experiments have been successful in usingmicrowaves at distances of several tens of meters to wirelessly transferelectric power. In the near future, it is expected that all electronicproducts will be wirelessly charged without electric wires anywhere andanytime.

Transfer of electric power using electromagnetic induction is a schemethat transfers electric power between a first coil and a second coil.When a magnet is moved in a coil, induction current occurs. By using theinduction current, a magnetic field is generated at a transferring end,and electric current is induced according to a change of the magneticfield so as to create energy at a reception end. This is referred to asmagnetic induction phenomenon, and a method of transferring electricpower using magnetic induction has remarkable energy transferefficiency.

In the resonance scheme, a system for wirelessly transferringelectricity by using the electric power transfer principle at a distanceof several meters from a charging device in a Coupled Mode Theory hasbeen developed. This wireless charging system resonates electromagneticwaves, and since a part of the resonated electric energy is directlytransferred to a device having an identical resonance frequency when thedevice having the identical resonance frequency appears, and residualwaves are absorbed again into an electromagnetic field without adistribution in air, it seems that the resonated electric energy has noeffect on a peripheral machine or the human body different from otherelectromagnetic waves.

On the other hand, a wireless electric power receiver using aconventional resonance scheme includes a rectifier circuit forconverting received alternating current waves into direct current waves,and a DC-DC conversion circuit for regulating electric power of therectified direct waves to a predetermined voltage value. However,because the DC-DC conversion circuit must use a manual element with alarge external value, there is a difficulty in that the circuit isimplemented to have a small mounting surface, a high capacity and a highefficiency. In a case where the wireless electric power receiver isimplemented in a mobile communication device, an increase of themounting surface has a negative effect on the thickness of the mobilecommunication device.

SUMMARY OF THE INVENTION

The present invention has been made to address the above mentionedproblems and disadvantages, and to provide at least the advantagesdescribed below. Accordingly, an aspect of the present invention is toprovide a wireless electric power receiver for controlling receivedwireless electric power by using a switch, thereby regulating themagnitude of the wireless electric power.

In accordance with an aspect of the present invention, a wirelesselectric power receiver for receiving wireless electric power from awireless electric transmitter is provided. The wireless electric powerreceiver includes an electric power receiving unit that receives thewireless electric power from the wireless electric power transmitter; arectifying unit that rectifies wireless electric power in a form ofalternate current output from the wireless electric power receiving unitand outputs rectified electric power; and an electric power regulationunit that receives an input of the rectified electric power, outputsfirst electric power which has a lower value of a first voltage thanthat of the rectified electric power for a first period, and does notoutput electric power for a second period, so as to output electricpower with a predetermined voltage value.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of the presentinvention will be more apparent from the following detailed descriptiontaken in conjunction with the accompanying drawings, in which:

FIG. 1 is a conceptual view illustrating operation of a wirelesscharging system;

FIG. 2 is a block diagram illustrating a wireless electric powertransmitter and a wireless electric power receiver according to anembodiment of the present invention;

FIG. 3 is a block diagram illustrating a wireless electric powerreceiver according to a related art, in which the wireless electricpower receiver is shown to be compared with the present invention;

FIG. 4 is a block diagram illustrating a wireless electric powerreceiver according to the present invention;

FIGS. 5A to 5C are circuit diagrams illustrating the wireless electricpower receiver according to embodiments of the present invention;

FIGS. 6A and 6B are graphs illustrating a voltage of an output terminalin a continuous current mode and a non-continuous current mode,respectively;

FIGS. 7A and 7B are graphs illustrating a voltage of an output terminalin a continuous current mode and a non-continuous current mode,respectively;

FIG. 8A is a block diagram illustrating a wireless electric powertransmitter and a wireless electric power receiver according to anembodiment of the present invention;

FIG. 8B is a circuit diagram illustrating the wireless electric powertransmitter and the wireless electric power receiver according to anembodiment of the present invention;

FIG. 9 is a circuit diagram illustrating the wireless electric powerreceiver according to the present invention;

FIG. 10 is a circuit diagram illustrating a method of generating acontrol signal to turn on/off a switch according to an embodiment of thepresent invention;

FIG. 11 is a graph illustrating generation of the control signalaccording to an embodiment of the present invention;

FIG. 12 is a circuit diagram illustrating a boost bias generatoraccording to an embodiment of the present invention; and

FIG. 13 is a graph illustrating a voltage applied to the boost biasgenerator.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE PRESENT INVENTION

Hereinafter, various embodiments of the present invention will bedescribed with reference to the accompanying drawings. It should benoted that the same components of the drawings are designated by thesame reference numeral throughout the drawings and description. In thefollowing description of the present invention, a detailed descriptionof known functions and configurations incorporated herein will beomitted when it may make the subject matter of the present inventionunclear.

FIG. 1 is a conceptual view illustrating operation of a wirelesscharging system. As shown in FIG. 1, the wireless charging systemincludes a wireless electric power transmitter 100 and one or morewireless electric power receivers 110-1, 110-2, . . . , and 110-n.

The wireless electric power transmitter 100 wirelessly transmitselectric power 1-1, 1-2, . . . , and 1-n to the one or more wirelesselectric power receivers 110-1, 110-2, . . . , and 110-n. Moreparticularly, the wireless electric transmitter 100 may wirelesslytransmit electric power 1-1, 1-2, . . . , and 1-n to only wirelesselectric power receivers which are certificated through a predeterminedcertification procedure.

The wireless electric power transmitter 100 is electrically connected tothe wireless electric power receivers 110-1, 110-2, . . . , and 110-n.For example, the wireless electric power transmitter 100 may transmitwireless electric power in a form of electromagnetic waves to thewireless electric power receivers 110-1, 110-2, . . . , and 110-n.

On the other hand, the wireless electric power transmitter 100 iscapable of performing a bidirectional communication with the wirelesselectric power receivers 110-1, 110-2, . . . , and 110-n. Here, thewireless electric power transmitter 100 and the wireless electric powerreceivers 110-1, 110-2, . . . , and 110-n process packets 2-1, 2-2, . .. , 2-n including a predetermined number of frames, or transmit andreceive the packets. The above mentioned frames will be described indetail below. The wireless electric power receiver may be implemented ina mobile communication terminal, a PDA, a PMP, a smartphone and thelike.

The wireless electric power transmitter 100 is capable of wirelesslyproviding electric power to a plurality of wireless electric powerreceivers 110-1, 110-2, . . . , and 110-n. For example, the wirelesselectric power transmitter 100 is capable of wirelessly transmittingelectric power to a plurality of wireless electric power receivers110-1, 110-2, . . . , and 110-n in a resonance manner. Where thewireless electric transmitter 100 employs the resonance scheme, adistance between the wireless electric power transmitter 100 and theplurality of wireless electric power receivers 110-1, 110-2, . . . , and110-n is preferably within about 30 m. Where the wireless electrictransmitter 100 employs the electromagnetic induction resonance scheme,a distance between the wireless electric power transmitter 100 and theplurality of wireless electric power receivers 110-1, 110-2, . . . , and110-n is preferably within about 10 cm.

The wireless electric power receivers 110-1, 110-2, . . . , and 110-nwirelessly receive electric power from the wireless electric powertransmitter 100 and charge a battery included in a mobile terminal.Further, the wireless electric power receivers 110-1, 110-2, . . . , and110-n transmit a signal to request a wireless electric transmission,information necessary for a reception of wireless electric power,information on a status of the wireless electric power receivers, orinformation on a control of the wireless electric power transmitter 100,to the wireless electric power transmitter 100. The information on thetransmission signal will be described in detail later.

Furthermore, the wireless electric power receivers 110-1, 110-2, . . . ,and 100-n transmit a message indicating a charged status of eachreceiver to the wireless electric power transmitter 100.

The wireless electric power transmitter 100 may include an indicatingmeans such as a display unit, and display the status of each of thewireless electric power receivers 110-1, 110-2, . . . , and 110-n, basedon the message received from each of the wireless electric powerreceivers 110-1, 110-2, . . . , and 110-n. In addition, the wirelesselectric power transmitter 100 may display an expected time until therespective wireless electric power receivers 110-1, 110-2, . . . , and110-n are charged.

The wireless electric power transmitter 100 may transmit a controlsignal to disable the wireless charging function of the wirelesselectric receivers 110-1, 110-2, . . . , and 110-n. When receiving acontrol signal to disable the wireless charging function from thewireless electric power transmitter 100, the wireless electric powerreceivers are capable of disabling the wireless charging function.

FIG. 2 is a block diagram illustrating a wireless electric powertransmitter and a wireless electric power receiver according to anembodiment of the present invention.

As shown in FIG. 2, the wireless electric power transmitter 200 includesan electric power transmitting unit 211, a controller 212 and acommunication unit 213. Further, the wireless electric receiver 250includes an electric power receiving unit 251, a controller 252 and acommunication unit 253.

The electric power transmitting unit 211 is capable of supplyingelectric power which is required by the wireless electric powertransmitter 200, and wirelessly provides electric power to the wirelesselectric receiver 250. Here, the electric power transmitting unit 211provides electric power in a form of alternating current (AC) waves, andalso may supply electric power in a form of direct current (DC) waves.Furthermore, the electric power transmitting unit 211 converts the DCwaves into the AC waves by using an inverter so as to provide theelectric power in the form of alternating current. The electric powertransmitting unit 211 may be implemented in the form of an embeddedbattery or in the form of an electric power receiving interface so as toreceive electric power from outside thereof and supply electric power tothe other structural elements. It will be easily understood by a personskilled in the art that the electric power transmitting unit 211 is notlimited if it supplies electric power as constant AC waves.

In addition, the electric power transmitting unit 211 may supply the ACwaves to the wireless electric receiver 250 in the form ofelectromagnetic waves. The electric power transmitting unit 211 furtherincludes an additional loop coil, resulting in a transmission or areception of desired electromagnetic waves. Where the electric powertransmitting unit 211 is implemented by the loop coil, an inductance Lof the loop coil may be varied. On the other hand, it will be easilyunderstood by a person skilled in the art that the electric powertransmitting unit 211 is not limited as a means for transmitting andreceiving the electromagnetic waves.

The controller 212 controls the overall operation of the wirelesselectric power transmitter 200, by using an algorithm, a program, or anapplication which is required for a control and read from a storage unit(not shown). The controller 212 may be implemented in a form of a CPU, amicroprocessor, a mini computer and the like. Operation of thecontroller 212 will be described in detail later.

The communication unit 213 communicates with the wireless electric powerreceiver 250 in a specific manner. The communication unit 213 is capableof communicating with communication unit 253 of the wireless electricpower receiver 250 by using a Near Field Communication (NFC) scheme, aZigbee communication scheme, an infrared ray communication scheme, avisible ray communication scheme, a Bluetooth communication scheme, aBluetooth low energy scheme, and the like. The communication unit 213according to the embodiment of the present invention is capable ofperforming communication by using the Bluetooth low energy scheme. Inaddition, the communication unit 213 may use a CSMA/CA algorithm. Aselection of frequency and channel which the communication unit 213 useswill be described in detail later. On the other hand, the abovementioned communication schemes are merely illustrative, and the scopeof the present invention is not limited by a specific communicationscheme which is performed by the communication unit 213.

Furthermore, the communication unit 213 may transmit a signal forinformation of the wireless electric power transmitter 200. Here, thecommunication unit 213 is capable of performing a unicast, a multicast,or a broadcast.

The communication unit 213 receives electric power information from thewireless electric power receiver 250. Here, the electric powerinformation may include at least one of a capacity of the wirelesselectric power receiver 250, a remaining capacity of a battery,frequency of charges, the amount of used battery capacity, a batterycapacity and a used (or remaining) proportion of the battery. Further,the communication unit 213 transmits a signal to control a chargingfunction of the wireless electric power receiver 250. The signal tocontrol the charging function may be a control signal of controlling thewireless electric power receiving unit 251 of the specific wirelesselectric power receiver 250 so as to enable or disable the chargingfunction.

The communication unit 213 may receive a signal from another wirelesselectric power transmitter (not shown) as well as the wireless electricpower receiver 250. For example, the communication unit 213 may receivea notice signal of the frame in the above mentioned FIG. 1 from anotherwireless electric power transmitter.

On the other hand, in FIG. 2, it is shown that the electric powertransmitting unit 211 and the communication unit 213 are configured withdifferent hardware, and the wireless electric power transmitter 200communicates in an out-band manner, but it is merely illustrative. Inthe present invention, the electric power transmitting unit 211 and thecommunication unit 213 are implemented with one piece of hardware sothat the wireless electric power transmitter 200 performs communicationin an in-band manner.

The wireless electric power transmitter 200 and the wireless electricpower receiver 250 transmit and receive various signals. Accordingly,the wireless electric power receiver 250 enters a wireless electricpower network which is managed by the wireless electric powertransmitter 200 and performs a charging process through wirelesselectric power transmission and reception. The above mentioned processwill be described in detail later.

FIG. 3 is a block diagram illustrating a wireless electric powerreceiver according to a related art, in which the wireless electricpower receiver is shown to be compared with the present invention.

As shown in FIG. 3, the wireless electric power receiver 250 includes anelectric power receiving unit 251, a controller 252, a communicationunit 253, a rectifying unit 254, a DC/DC converter 255, a switching unit256 56 and a charging unit 257.

A description of the electric power receiving unit 251, the controller252 and the communication unit 253 was described above and will beomitted herein. The rectifying unit 254 is capable of rectifyingwireless electric power received in the electric power receiving unit251 in the form of direct current, and is implemented in a form ofbridge diode. The DC/DC converter 255 converts the rectified electriccurrent into a predetermined gain. For example, the DC/DC converter 255converts the rectified electric current so that a voltage at an outputend 259 becomes 5V.

The switching unit 256 connects the DC/DC converter 255 to the chargingunit 257. The switching unit 256 is held in an on/off state under thecontrol of the controller 252. When the switching unit 256 is in the onstate, the charging unit 257 stores converted electric power which isinput from the DC/DC converter 255.

However, the wireless electric power receiver 250 according to acomparison example which is compared with the present invention includesthe DC/DC converter 255. Accordingly, the number of manual elements andIntegrated Circuits increase, and it is difficult to miniaturize thewireless electric power receiver 250.

FIG. 4 is a block diagram illustrating a wireless electric powerreceiver according to an embodiment of the present invention.

As shown in FIG. 4, the wireless electric power receiver 400 includes anelectric power receiving unit 410, a rectifying unit 420, an electricpower regulating unit 430 and a rod unit 430.

The electric power receiving unit 410 receives electric power from anwireless electric power transmitter (not shown). The rectifying unit 420rectifies electric power in the form of alternate current (AC) which isreceived from the electric power receiving unit 410 and outputs theelectric power in a form of direct current (DC). The electric powerregulating unit 430 converts and regulates the rectified electric powerhaving a predetermined value, for example a voltage of 5V, and thenoutputs the electric power. The load unit 440 may store the electricpower.

In particular, the electric power regulating unit 430 outputs firstelectric power with a first voltage value for a first period, and secondelectric power with a second voltage value for a second period. Thus,the electric power regulating unit 430 outputs electric power with thepredetermined value, for example the voltage of 5V. Furthermore, theelectric power regulating unit 430 does not include converting meanswhich has a manual element, and is capable of converting the voltagevalue of the electric power merely based on an on/off regulation of theswitch. Accordingly, it is possible to miniaturize and make the wirelesselectric power receiver light weight in comparison with the conventionalDC-DC conversion circuit. According to an embodiment of the presentinvention, the total number of manual elements and Integrated Circuitscan be remarkably reduced. Further, the wireless electric power receiverincludes a resonance type inductor and capacitor as well as a switch,thereby obtaining stable direct current electric power. Moreover, it ispossible to provide more exact and stable direct current electric power.

FIG. 5A is a circuit diagram illustrating the wireless electric powerreceiver according to the embodiment of the present invention. Morespecifically, the embodiment of FIG. 5A is a circuit diagram of thewireless electric power receiver 400 in the first period shown in FIG.4.

As shown in FIG. 5A, the wireless electric power receiver includes aresonance circuit 510, a rectifying circuit 520, a first switch 532, asecond switch 533, a third switch 534, a first capacitor 536, and asecond capacitor 537.

The resonance circuit 510 includes a capacitor 511 and an induction coil512, and receives electric power with a value of I_(RS) from thewireless electric power transmitter based on a resonance scheme.

The rectifying circuit 520 includes at least one diode, and rectifiesand converts the alternate current electric power, which is input fromthe resonance circuit 510, into direct current so as to output theelectric power. The rectifying circuit 520 outputs the rectifiedelectric power which has a current value of I_(RT) and a voltage valueof V_(XH).

The rectifying circuit 520 is connected to a first node 531. The voltagevalue of V_(XH) is applied to the first node 531. The first node 531 isconnected to the first switch 532 and the second capacitor 537. Thesecond capacitor 537 has an electrostatic capacity of C_(FL). Here, thefirst capacitor 536 and the second capacitor 537 may be variablecapacitors, and the electrostatic capacities C_(out) and C_(FL) may bechanged. As the electrostatic capacities of the first capacitor 536 andthe second capacitor 537 are adjusted, an output voltage is adjusted inthe second period (OFF duty). The electrostatic capacities C_(out) andC_(FL) use a voltage division, and may be called a capacitive voltagedivider. In addition, it is possible to use a capacity value which isnecessary for a regulation in the first period (ON duty) according tothe transmitted electric power. The first period (ON duty) and thesecond period (OFF duty) will be described in detail later.

The first switch 532, the second switch 533 and the third switch 534 maybe implemented with a high-side PMOS switch or a low-side NMOS switch.Accordingly, an integration of the first switch 532, the second switch533, the third switch 534 and a rectifying circuit is possible.

One end of the first switch 532 is connected to the first node 531, andthe other end of the first switch 532 is connected to one end of thefirst capacitor 536. For the first period, the first switch 532 iscontrolled to be on, and thus the rectifying circuit 520 may beconnected to one end of the first capacitor 536. On the other hand, theother end of the second capacitor 537 is connected to a second node 535,and the second node 535 is connected to one end of the second switch 533and one end of the third switch 534. The other end of the second switch533 is connected to the other end of the first switch 532 and one end ofthe first capacitor 536. In particular, the second switch 533 iscontrolled to be in the off state for the first period. The second node535 is connected to one end of the third switch 534, and the other endof the third switch 534 is connected to the other end of the firstcapacitor 536 and a ground. For the first period, the third switch 534is controlled to be in an on state, and thus the other end of the secondcapacitor 537 is connected to ground. That is, for the first period, thefirst switch 532 and the third switch 534 are controlled to be in an onstate, and the second switch 533 is controlled to be in an off state.Therefore, the voltage value of V_(XH) applied to the first node 531 maybe dispersed to the first capacitor 536 and the second capacitor 537.This is caused by a parallel connection of the first and secondcapacitors 536 and 537. Thus, a voltage value of the first capacitor 536has a smaller value than the voltage value of V_(XH) shown in FIG. 6A,which shows a graph of a voltage value applied to the output end for thefirst period. As shown in FIG. 6A, a voltage V_(out) of the output endis lower than the voltage value of V_(XH) for the first period (ONduty).

FIG. 5B is a circuit diagram illustrating the wireless electric powerreceiver according to an embodiment of the present invention. Morespecifically, the embodiment of FIG. 5B is the circuit diagram of thewireless electric power receiver 400 in the second period shown in FIG.4.

FIG. 5B shows only the right side of the rectifying circuit 520 of FIG.5A. For the second period, as shown in FIG. 5B, the first and thirdswitches 532 and 534 are controlled to be in an off state, and thesecond switch 533 is controlled to be in an on state. Therefore, thefirst node 531 is connected to the second capacitor 537, and the secondcapacitor 537 is connected to the first capacitor 536. As a result, thevoltage value of V_(HX) applied to the first node 531 is applied to thefirst capacitor 536. Thus, the first capacitor 536, which is the outputend, has the voltage value of V_(XH) shown in FIG. 6A. This is caused bythe serial connection of the first and second capacitors 536 and 537.FIG. 6A shows a graph of the voltage value applied to the output end forthe second period. As shown in FIG. 6A, the voltage V_(out) of theoutput end is the voltage value of V_(XH) for the second period (OFFduty). As described above, the capacitor 536 has a smaller outputvoltage than the voltage value of V_(XH) for the first period, and hasthe output voltage value of V_(XH) for the second period, so as tooutput a predetermined voltage value, for example 5V, for a totalperiod.

On the other hand, an output voltage mode of the first and secondperiods may be referred to as a Continuous Current Mode (CCM). FIG. 7Ais a graph showing the current in the CCM. As shown in FIG. 7A, I_(RS)and I_(RT) increase for the first period (ON duty), while decreasing forthe second period (OFF duty). However, the current for the first andsecond periods may be continuous. The increasing of the current for thefirst period (ON duty) is caused by an increase of the transmittedelectric power due to a decrease of equivalent impedance in view of thewireless electric power transmitter. On the other hand, the decreasingof the current for the second period (OFF duty) is caused by a decreaseof the transmitted electric power due to an increase of the equivalentimpedance in view of the wireless electric power transmitter. The CCMmay be used when the transmitted electric power is large, and aDiscontinuous Current Mode (DCM) may be used when the transmittedelectric power is small.

FIG. 5C is a circuit diagram for the second period in a DCM. The circuitdiagram for the first period in the DCM may be identical to that asshown in FIG. 5A. For the second period, as shown in FIG. 5C, the first,second and third switches 531, 532 and 534 are controlled to be in theoff state. Therefore, the voltage applied to the first capacitor 536,which is the output end, has a value attenuating from the voltage valueof V_(XH), as shown in FIG. 6B. That is, the voltage value which islower than V_(XH) is output for the first period, and the voltage valuewhich attenuates from the V_(XH) is output for the second period.Accordingly, the predetermined voltage, i.e. a voltage value of 5V, maybe output for the total period.

FIG. 7B is a graph showing a value of current in the DCM. As shown inFIG. 7B, I_(RS) and I_(RT) have a value of zero for the second period.This is caused by the voltage value of V_(XH) in “a floating state”. Thephrase “floating state” means a state in that an electric power sourceand ground which are capable of inducing an electric potentialdifference are not connected to each other, and a meaning of “floatingstate” will be clearly understood by a person skilled in the art.

As described above, although a manual element is not included in the CCMor DCM, the predetermined voltage, i.e. the voltage value of 5V, isstably maintained and output. The phrases “n*147 ns” and “(8−n)*147 ns”shown in FIGS. 7A and 7B mean that a period is 147 ns in the case that afrequency of 6.78 MHz (a carrier frequency satisfying a standard ofA4WP) is used, and an on/off duty is controlled to be eight times ofperiod. However, it should be understood that the frequency of 6.78 MHzis an example for the description of the present invention.

FIG. 8A is a block diagram illustrating the wireless electric powertransmitter and the wireless electric power receiver according to anembodiment of the present invention.

As shown in FIG. 8, the wireless electric power transmitter 800 includesan electric power transmitting unit 811, a controller 812, acommunication unit 813 and an electric power supplying unit 814. Inaddition, the wireless electric power receiver 850 includes an electricpower receiving unit 851, a communication unit 853, a rectifying unit860, an electric power regulation unit 870 and a load unit 880. Theelectric power regulation unit 870 includes a switching unit 871 and acontroller 872.

The electric power supplying unit 814 supplies electric power to theelectric power transmitting unit 811, and an amount of supplied electricpower is controlled by the controller 812. The electric powertransmitting unit 811 is capable of wirelessly transmitting electricpower to the electric power receiving unit 851 based on the resonancescheme.

The rectifying unit 860 rectifies input electric power, and outputs therectified electric power to the electric power regulation unit 870. Inparticular, the rectifying unit 860 outputs the rectified electric powerto the switching unit 870. The switching unit 870 includes at least oneswitch, and may output first electric power having a first voltage valueor second electric power having a second voltage value, based on anon/off state of the switch. The electric power having the predeterminedvoltage, i.e. the voltage value of 5V, is output from the electric powerregulation unit 870 as the first electric power and the second electricpower.

The controller 872 receives an input of partial electric power from therectifying unit 860. The controller 872 controls the on/off state ofeach switch included in the switching unit 870, based on the partialelectric power input from the rectifying unit 860. The controller 872controls the on/off state of each switch included in the switching unit870 so that the first electric power having the first voltage value isoutput for the first period, or so that the second electric power havingthe second voltage value is output for the second period. Further, thecontroller 872 controls the on/off state of each switch included in theswitching unit 870 so that the electric power having the predeterminedvoltage value, i.e. a voltage value of 5V, is output.

When excessive electric power is applied to the rectifying unit 860, thecontroller 872 controls the communication unit 853 to transmit a signal,which adjusts electric power output from the electric power supplyingunit 814, to the communication unit 813.

The load unit 880 receives an input of electric power having apredetermined voltage value, i.e. a voltage value of 5V, output from theswitching unit 870.

FIG. 8B is a circuit diagram illustrating the wireless electric powertransmitter and the wireless electric power receiver according to anembodiment of the present invention.

In FIG. 8B, the electric power supplying unit 814 includes electricpower supplying means, a class E Amp, and an inverter. The electricpower supplying means is variable in a range of 10V to 14V. The electricpower transmitting unit 811 may include a resonance circuit. Here, theresonance frequency may be, for example, 6.78 Mhz.

The electric power receiving unit 851 wirelessly receives the electricpower in resonance frequency of, for example, 6.78 Mhz, and includes aresonance circuit. The rectifying unit 860 includes first to fourthdiodes 861, 862, 863 and 864, and a third capacitor 865 having anelectrostatic capacity of C_(LM). Signals of both ends of the thirdcapacitor 865 are input into a timing controller 844. The timingcontroller 844 generates and outputs a clock signal (CLK) forcontrolling the on/off state of the first, second and third switches874, 877 and 878. The timing controller 844 generates the clock signalbased on a delay signal 881, a mode selection signal 882 and a dutysignal 883. A gate driving signal generating element 885 generates andoutputs a gate driving signal based on the clock signal. In addition,the gate driving signal generating element 885 may generate the gatedriving signal by using an output result of the comparator 888 and thecalculator 887. The generation of the gate driving signal will bedescribed in detail later.

On the other hand, the on/off states of the first, second and thirdswitches 874, 877 and 878 are controlled based on the clock signal.Based on the on/off states of the first, second and third switches 874,877 and 878, for example, the first voltage is applied to an output end879 for the first period, and the second voltage value is applied to anoutput end 879 for the second period.

FIG. 9 is a circuit diagram illustrating the wireless electric powerreceiver according to an embodiment of the present invention. Withrelation to FIG. 9, only additional structural elements will bedescribed in comparison with FIG. 5A. Referring to FIG. 9, the wirelesselectric power receiver may include a first resistor 901, a secondresistor 902, a comparator 903, a switch controller 904 and a signaldetector 905.

The first resistor 901 has one end connected to an output end, and otherend connected to one end of the second resistor 902 and a first inputterminal (−) of the comparator 903. The other end of the second resistor902 is connected to ground. A reference voltage V_(ref) is applied tothe second input terminal (+) of the comparator 903. The comparator 903compares the reference voltage V_(ref) with the voltage applied to thefirst input terminal (−), and outputs a comparison result to the switchcontroller 904. The switch controller 904 controls the on/off state ofeach of the first, second and third switches 532, 533 and 534 based onthe comparison result. The signal detector 905 receives a feedback of anAC synchronization signal from the resonance circuit 510, and outputsthe AC synchronization signal to the switch controller 904. The switchcontroller 904 controls the on/off states of each of the first, secondand third switches 532, 533 and 534 based on the comparison result. Forexample, the reference voltage V_(ref) of the comparator 903 may be setto 5V. When a voltage higher than the reference voltage of 5V is appliedto the output end, the electric power regulation unit 870 controls theon/off state of the switch so that the voltage applied to the output endis held to a voltage of 5V. Referring to FIGS. 5A and 5B, as describedabove, for the first period in which the first and third switches 532and 534 are controlled to be in the on state and the second switch 533is controlled to be in the off state, the relatively low voltage isapplied to the comparator 903. Moreover, for the second period in whichthe first switch 532 and the third switch 534 are controlled to be inthe off state, and the second switch is controlled to be in the onstate, a relatively high voltage is applied to the comparator 903. Theelectric power regulation unit 870 sets the first period to berelatively longer than an existing period, and regulates the voltage ofthe output end so that the voltage of 5V is constantly applied to theoutput end. Otherwise, where a voltage lower than the reference voltageof 5V is applied to the output end, the electric power regulation unit870 sets the first period to be relatively short and regulates thevoltage of the output end so that the voltage applied to the output endis held to a voltage of 5V.

On the other hand, in DCM, electric power is output for the first periodwhile not being output for the second period. Where a voltage higherthan the reference voltage of 5V is applied to the output end, theelectric power regulation unit 870 sets the first period to berelatively short and regulates the voltage of the output end so that thevoltage applied to the output end is held to a voltage of 5V. Further,where a voltage lower than the reference voltage of 5V is applied to theoutput end, the electric power regulation unit 870 sets the first periodto be relatively long and regulates the voltage of the output end sothat the voltage applied to the output end is held to a voltage of 5V.

FIG. 10 is a circuit diagram illustrating a method of generating aswitch on/off control signal according to an embodiment of the presentinvention. The operation of the circuit shown in FIG. 10 will bedescribed with reference to FIG. 11. FIG. 11 is a graph illustrating ageneration of the control signal according to an embodiment of thepresent invention.

The rectifying unit 860 includes first to fourth diodes 1061, 1062, 1063and 1064, and a third capacitor 1065 having an electrostatic capacity ofC_(LM). A node 1066 is disposed between the first diode 1061 and thethird diode 1063, and a node 1067 is disposed between the second diode1062 and the fourth diode 1064. A V_(IN+) is applied to the node 1066,and a V_(IN−) is applied to the node 1067. Differential signals of theV_(IN+) and the V_(IN−) in FIG. 11 are applied to the node 1066 and thenode 1067, respectively.

The node 1066 may be connected to one end of a resistor 1011, and otherend of the resistor 1011 may be connected to one end of a resistor 1012.The other end of the resistor 1012 may be connected to ground. The otherend of the resistor 1011 and the one end of the resistor 1012 isconnected to a first input terminal (+) of the calculator 1013. On theother hand, one end of a resistor 1019 and one end of a resistor 1014are connected to a second input terminal (−) of the calculator 1013. Theother end of the resistor 1019 may be connected to node 1067, and theother end of the resistor 1014 may be connected to one end of acapacitor 1015. The other end of the capacitor 1015 may be connected toground.

Accordingly, differential signals of a V_(IN+) and a V_(IN−) are inputinto the first input terminal (+) and the second input terminal (−) ofthe calculator 1013, respectively. The calculator 1013 calculates thedifferential signals to be input, and outputs a compositesynchronization signal (Comp Sync) 1016. In FIG. 11, the compositesynchronization signal may be generated by calculating the differentialsignals of the V_(IN+) and the V_(IN−).

The node 1067 is also connected to an inverter 1017. The inverter 1017inverts a signal V_(IN−) applied to the node 1067 and outputs aninverted synchronization signal (Inv Sync) 1018. In FIG. 11, theinverted synchronization signal (Inv Sync) is inverted and generated bythe signal V_(IN−). On the other hand, a selection signal (SEL) isapplied to the switch 1023 to enable the switch to determine whether toreceive the composite synchronization signal or the invertedsynchronization signal. For example, the selection signal (SEL) controlsthe switch 1023 to receive the inverted synchronization signal for thefirst period (ON duty), and to receive the composite synchronizationsignal for the second period (OFF duty).

The delay unit 1020 delays the inverted synchronization signal (InvSync) or the composite synchronization signal so as to output a clocksignal. As shown in FIG. 11, a clock signal (CLK) in which the invertedsynchronization signal (Inv Sync) is delayed is generated for the firstperiod (ON duty), and a clock signal (CLK) in which the compositesynchronization signal (Comp Sync) is delayed is generated for thesecond period (OFF duty).

FIG. 12 is a circuit diagram illustrating a boost bias generatoraccording to an embodiment of the present invention. For example, theboost bias generator shown in FIG. 12 may be connected to the node 531of FIG. 5A and FIG. 9 and the output end V_(out) FIG. 9.

An Edge Enhancement Filter (EEF) 1210 and a Schottky diode 1202 may beconnected to the node 1201. The EEF 1210 includes a capacitor 1211, aresistor 1212 and a resistor 1213. The capacitor 1211 has, for example,an electrostatic capacity of 50 fF (femto Farad), the resistor 1212 has,for example, a resistance value of 700Ω, and the resistor 1213 has, forexample, a resistance value of 10 kΩ. The EEF 1210 may be connected tothe third sub-switch 1221. The third sub-switch 1221 is implemented withan FET, and the EEF 1210 is connected to a gate end of the thirdsub-switch 1221. A drain of the third sub-switch 1221 is connected to agate of the first sub-switch 1223. A source of the third sub-switch 1221is connected to a diode 1227 and a source of the second sub-switch 1224.A drain and a gate of a second sub-switch 1224 are connected to a sourceof a first sub-switch 123 and a node 1225. A capacitor 1226 is disposedbetween node 1225 and V_(B). The Schottky diode 1202 may be connected toa drain of the first sub-switch 1223. In addition, a plurality of diodes1227 are present, and for example, five diodes are employed.

In a case where switches 532, 533 and 534 of FIG. 9 are implemented witha N type MOSFET, for example, the boost bias generator is held to apredetermined voltage higher than a voltage V_(out) of the output end tooperate. The boost bias generator may generate a voltage tosubstantially operate the first switch 532 of FIG. 9. In the CCM mode,especially, when a high voltage is applied to V_(XH) with switchingbetween the V_(out) and a 2V_(out), a boost bias provides a high voltageto the first switch 532.

Furthermore, the boost bias generator may hold a voltage V_(B) appliedto the node 1225 below a predetermined voltage of, for example, 10V. Asshown in FIG. 13, the voltage V_(B) applied to the node 1225 is heldbelow the predetermined voltage of 10V. Therefore, the boost biasgenerator controls the switches 532, 533 and 534 to operate in a casewhere the switches 532, 533 and 534 are implemented with the N typeMOSFET, and controls the switches 532, 533 and 534 so that an excessivevoltage is not applied to the entire wireless electric power receiver.

For example, when a difference of a voltage of V_(G1) and a thresholdvoltage V_(th) of the first sub-switch 1223 is smaller than the voltageV_(B), the first sub-switch 1223 may turn on. Moreover, when adifference of a voltage of V_(G1) and a threshold voltage V_(th) of thefirst sub-switch 1223 is larger than the voltage V_(B), the firstsub-switch 1223 may turn off. The boost bias generator operates based onthe above mentioned operation.

While the present invention has been shown and described with referenceto certain embodiments thereof, it will be understood by those skilledin the art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the present invention asdefined by the appended claims. Therefore, various modifiedimplementations can be made without departing from the substance of thepresent invention claimed in the appended claims, and the modifiedimplementations should not be construed separately from the technicalidea or concept of the present invention.

What is claimed is:
 1. A wireless electric power receiver for receivingwireless electric power from a wireless electric transmitter, thewireless electric power receiver comprising: an electric power receivingunit that receives the wireless electric power from the wirelesselectric power transmitter; a rectifying unit that rectifies wirelesselectric power in the form of alternating current output from thewireless electric power receiving unit and outputs rectified electricpower; and an electric power regulation unit that receives an input ofthe rectified electric power, and outputs first electric power which hasa lower value of a first voltage than that of the rectified electricpower for a first period while outputting second electric power whichhas a second voltage of the rectified electric power for a secondperiod, so as to output electric power with a predetermined voltagevalue.
 2. The wireless electric power receiver as claimed in claim 1,wherein the electric power regulation unit increases impedance of thewireless electric power receiver for the first period, and reducesimpedance of the wireless electric power receiver for the second period.3. The wireless electric power receiver as claimed in claim 1, whereinthe electric power regulation unit increases electric power which isreceived by the wireless electric power receiving unit for the firstperiod, and reduces electric power which is received by the wirelesselectric power receiving unit for the second period.
 4. The wirelesselectric power receiver as claimed in claim 1, wherein the electricpower regulation unit includes: a node connected to an output end of therectifying unit; a first switch having one end connected to the node; afirst capacitor having one end connected to the node; a second switchhaving one end connected to another end of the first capacitor; a thirdswitch having one end connected to the another end of the firstcapacitor; and a second capacitor having one end connected to anotherend of the first switch and another end of the second switch, andanother end connected to another end of the third switch.
 5. Thewireless electric power receiver as claimed in claim 4, wherein theelectric power regulation unit controls the first and third switches tobe in an on state and the second switch to be in an off state, for thefirst period.
 6. The wireless electric power receiver as claimed inclaim 5, wherein the electric power regulation unit connects the firstcapacitor and the second capacitor in parallel, and controls the firstelectric power having the first voltage to be output.
 7. The wirelesselectric power receiver as claimed in claim 4, wherein the electricpower regulation unit controls the first and third switches to be in anoff state and the second switch to be in an on state, for the firstperiod.
 8. The wireless electric power receiver as claimed in claim 7,wherein the electric power regulation unit connects the first capacitorand the second capacitor in parallel, and controls the second electricpower having the second voltage to be output.
 9. The wireless electricpower receiver as claimed in claim 1, wherein the electric powerregulation unit includes a switch controller that controls the firstswitch, the second switch and the third switch based on at least one ofa voltage applied to an output end of the electric power regulationunit, and a synchronization signal received in the electric powerreceiving unit.
 10. The wireless electric power receiver as claimed inclaim 9, further comprising a comparator that compares the voltageapplied to the output end of the electric power regulation unit and areference voltage, and outputs a comparison result to the switchcontroller.
 11. The wireless electric power receiver as claimed in claim10, wherein the electric power regulation unit sets the first period tobe longer than an existing period if the voltage applied to the outputend of the electric power regulation unit is larger than the referencevoltage.
 12. The wireless electric power receiver as claimed in claim10, wherein the electric power regulation unit sets the first period tobe shorter than an existing period if the voltage applied to the outputend of the electric power regulation unit is smaller than the referencevoltage.